1. Field of the Invention
This invention relates to an anti-mirror-bounce device for a single-lens reflex camera having a main movable mirror which guides light flux coming through a photo-taking lens to a view finder, an auxiliary movable mirror which is arranged behind the main movable mirror to guide a part of the light flux to a light or distance measuring device and a mirror driving mechanism which is arranged to move these mirrors away from a photo-taking optical path.
2. Description of the Prior Art
Generally, in a single-lens reflex camera of the class having a main movable mirror which guides light flux coming through a photo-taking lens to a view finder and an auxiliary movable mirror which is arranged behind the main movable mirror to guide a part of the light flux to a light or distance measuring device, a mirror box is disposed behind the photo-taking lens. The main movable mirror which is either wholly or partially formed to be semitransparent is pivotally carried within the mirror box. The auxiliary movable mirror is also pivotally carried in the rear of the main movable mirror. A light flux which passes through the main movable mirror is reflected by the auxiliary movable mirror to be guided to a light sensitive element provided at the bottom of the mirror box for light or distance measurement. These movable mirrors are arranged to be sprung upward by the mirror driving mechanism away from a photo-taking optical path at the time of exposing a film to light for photographing. Upon completion of the photographing process, these mirrors are brought back to their predetermined original positions by means of a return spring and are stopped there by colliding with stoppers. However, when the return spring brings the main and auxiliary movable mirrors back to their original positions after photographing operation, these mirrors are caused to bounce to a considerable degree by the spring force of the return spring and the inertia of the movable mirrors as they come to abut on the stoppers. Particularly, the bounce of the movable mirrors is accelerated and complicated by an additional bounce of a driving lever in the case of a camera where movable mirrors are arranged to be uplifted in a retracting manner for the purpose of limiting the movable extent of movement of the main movable mirror for reduction in space requirement with the center of rotation of the main movable mirror arranged to be pivotally carried by the mirror driving lever and to have the mirror retracted in uplifting the mirror.
The bounce which takes place when the mirrors come back to their original positions makes it hardly possible to obtain good pictures through a high speed continuous photographing operation carried out with an automatic winding device, because in the case of high speed continuous photography, light measurement must be carried out within a short winding period. Then, the light flux which comes through the main movable mirror and is reflected by the auxiliary movable mirror is prevented from coming to the light sensitive element by the bounce of the auxiliary movable mirror thereby resulting in inaccurate light measurement or in the complete prevention of light measurement until the bounce is over. The bounce of mirrors thus makes high speed continuous photography virtually impossible. Further, in the case of a camera where the light flux which comes through the main movable mirror and is reflected by the auxiliary movable mirror is arranged to be guided to a distance measuring light sensitive element for distance measurement, this problem is more serious, because distance measurement generally requires a longer time than light measurement.
The prior art attempts to solve this problem include a Japanese Utility Model Application Laid-Open No. 54-70531 (the applicant: Asahi Kogaku) and another Japanese Utility Model Application Laid-Open No. 54-16223 (Nihon Kogaku). In accordance with these prior art attempts, a stopper which is disposed at the returning position of a movable mirror is arranged to be resilient so that the bounce of the movable mirror can be suppressed by absorbing the impact of the movable mirror inflicted on the stopper when the mirror comes to abut thereon in its returning position. However, the bounce of the movable mirror still cannot be suppressed to a sufficient extent to permit high speed continuous photography. Besides, the methods disclosed in these Japanese Utility Model Applications are intended to prevent the bounce of a single movable mirror and are not contrived for preventing the bounce of a plurality of bouncing parts including main and auxiliary movable mirrors and a driving lever which is arranged to drive the movable mirrors. Another anti-bounce method of the prior art for preventing a movable mirror from bouncing when it returns to its original position is disclosed in a Japanese Patent Application Laid-Open No. 54-105532 (the applicant: Canon). In this case, an anti-bounce device is arranged to positively prevent a mirror from bouncing in such a way as to tightly hold it, so that the mirror can be sufficiently prevented from bouncing to permit high speed continuous photography without any impediment. However, this arrangement of the prior art is also intended for a single movable mirror and is not applicable where bounce of a plurality of members must be suppressed.